Display device, and display control method

A display device comprising:

• an image generator configured to generate a service image to be visually recognized by an observer by outputting light for forming an image toward a reflector reflecting incident light toward the observer's eyes and superimposing the light on a scene;
• a receiver configured to receive the observer's operation of reducing a visibility of the image;
• a controller configured to control a visibility of the service image in accordance with the operation performed on the receiver;
• and
• an output device is configured to output information,
• wherein the controller is configured to cause the output device to output warning information in a case in which the operation of reducing the visibility to a predetermined degree is performed.